Hindered phenolic esters of cyclic amino carboxylic acids

ABSTRACT

Organic materials, particularly synthetic polymers such as polypropylene are protected against oxidation in air, thermal degradation or deterioration by including, in such substances, a stabilizing amount of antioxidant. The antioxidant is obtained by reacting (a) an Alpha , Beta -unsaturated ester of a hindered hydroquinone and (b) a heterocyclic secondary amine.

United States Patent Kleiner 51 Aug. 1, 1972 [54] HINDERED PHENOLIC ESTERS OF [56] References Cited CYCLI AMIN ARB XYL C 0 C 0 [C ACIDS OTHER PUBLICATIONS [72] Inventor: Eduard Kleiner, Dobbs Ferry, N.Y.

Riddle, Reactions of Acrylic Esters, Reinhold Publish- 1 Asslgnw g v s Cowl-anon, Ardsley, ing Corp., New York, N.Y., 1954, pp. 153- 171.

Primary Examiner-Alex Mazel [22] Flled' 1968 Assistant Examiner.lames H. Tumipseed PP 782,486 Attomey-Karl F. Jorda, Bruce M. Collins, Martin J.

Spellman, Jr. and Nestor W. Shust 52 vs. C]. ..260/268, 260/45.8, 260/239, [57] ABS'HMCT 260/243, 260/247.2,"260/287, 260/315, Organic materials, particularly synthetic polymers 260/2943, 260/326.l, 260/326.1I, such as polypropylene are protected against oxidation 260/326.13, 252/402 in air, thermal degradation or deterioration by including, in such substances, a stabilizing amount of antioxidant. The antioxidant is obtained by reacting (a) an 51 Int. Cl. ..C07d 51 70 afi-unsamrated ester a hindered hydmquinone and (b) a heterocyclic secondary amine.

[58] Field of Search ..260/268 R 4 Claims, No Drawings Pli-ENOLIC ESTERS F CYCLIC The present invention is concerned with novel compounds which are useful as antioxidants for organic materials and particularly, as antioxidants for synthetic polymers such as, for example, polypropylene, polyethylene, polystyrene, polyvinyl chloride, nylon and other polyamides, polyesters, cellulosics, polyacetals, polyurethanes, petroleum and wood resins, mineral oils, animal and vegetable fats, waxes, rubbers such as styrene-butadiene rubber (SBR), acrylonitrilebutadiene-styrene rubber (ABS), olefin-copolymers, ethylene-vinyl-acetate copolymers, polycarbonates, polyacrylonitrile, poly (4-methyl pentene-l) polymers, polyoxymethylenes, and the like. The present invention also relates to a novel procedure for preparing the aforesaid novel antioxidants and to stabilized compositions containing said novel antioxidants.

The prevention of oxidation of various organic materials is obviously of primary industrial concern and, therefore, antioxidants are used in or added to a wide variety of commercial products such as synthetic polymers of the type indicated supra, oils, plastic materials, etc., which are normally subject to oxidative deterioration.

The novel antioxidants of the present invention are represented by the following formulas:

1 l s l a 1 1 3 A NCCH and CH-CN B N([3|CH l R COOR OOR R1 R COOR I II wherein R is (lpwer) alkyl (lower) alkyl R,, R and R are each I-l, lower alkyl, phenyl, aralkyl or C,,,H ,,,COOR, where m is 0 to 6 and preferably 0 or 1 and aralkyl has up to 24 carbon atoms and preferably up to 12 carbon atoms,

A N- is a radical derived from a heterocyclic amine having one replaceable amine hydrogen and being selected from ethyleneimine, trimethyleneimine, pyrrolidines, piperidines, morpholines, thiomorpholines, 1 ,2,3,4-

tetrahydroquinolines, indolines, isoindolines, carbazoles, N-alkylpiperazines, N-arylpiperazines and N-aralkylpiperazines, said alkyl, aryl and aralkyl group; having up to about 12 carbon atoms, v

N B N is a radical derived from a heterocyclic amine having two replaceable amine hydrogens and being selected from piperazines and 4, 4' polymethylenedipiperidines.

The heterocyclic secondary amines may be substituted by a halogen, alkyl, aryl, aralkyl, alkoxy, hydroxyl, alkylthio or carboalkoxy group or be part of an aliphatic or aromatic ring system. From the above it should be apparent that any heterocyclic secondary amine may be employed in preparing the novel compounds of this invention. The substituents on the heterocyclic rings are of no substantial consequence as long as they do not interfere with the reaction. The presence of tertiary amines either in the ring or outside similarly do not affect the reaction.

As used herein, alkyl is meant to cover groups containing from one to 24 carbon atoms; lower alkyl covers groups containing one to six carbon atoms, alkoxy covers groups containing from one to four carbon atoms. Further, the aryl group referred to above may be substituted by a halogen (chlorine or bromine), alkyl, alkoxy, hydroxyl, alkylthio or a carboalkoxy group. Aralkyl is meant to cover a group such as benzyl which may be substituted by a halogen (chlorine or bromine), alkyl, alkoxy, hydroxyl, alkylthio or a carboalkoxy group.

The novel antioxidants of the present invention are addition products of (a) an a,B-unsaturated ester of a hindered hydroquinone of the formula and (b) heterocyclic secondary amines of the formula A NH and HN B NH, wherein R, R R R and A N- and N B N- are as defined above.

The addition reaction of a heterocyclic secondary amine with an a,,8-unsaturated ester is accomplished by simply reacting the two reactants in equimolar quantities at room temperature in an inert solvent for from a few hours to a few days. For practical reasons, however, it is preferable to carry out the reaction at a temperature of from about 50 C to about 120 C. This reaction is more fully described in Reactions of the Acrylic Esters by EB. Riddle, p. 153-171, (Reinhold Publishing Corp., New York, N.Y., 1954).

The novel antioxidants of this invention were prepared by the following general procedure.

Equimolar amounts of the a,,8-unsaturated ester and the amine were dissolved in five times the amount of chloroform, sealed in an ampule under nitrogen and heated for 8 hours in an oil bath at 80 C. The reaction mixture was then filtered through five times the amount of neutral aluminum oxide and the crude reaction product was purified by crystallization as indicated in Table l. Yields are generally high, i.e., above percent.

Non-heterocyclic primary and secondary amines can also be added to the a,B-unsaturated esters to provide antioxidants. However, heterocyclic secondary amines 0 O O R wherein R is (lc| wer) alkyl (lower) alkyl and R R and R are as defined above. Examples of such esters are:

4 d. Bis(3,5-di-tert-butyl-4-hydroxyphenyl) itaconate CH=C-COOR0 H2 C 00110 Esters of: R R, R,

5 wherein R is i (C z): acrylic acid H -H -H methacrylic acid H H -cI-i, crotonic acid CH, H -H cinnamic acid C.H H H fumaric acid -co(iiz H H 10 C(Cm)" g f gl :g :g :3 The aforesaid afi-unsaturated esters (identified citraeonie acid H -'COOR CH, above as compoun and are reacted itaconic acid H H CH COOR aconific acid COOR with the following heterocyclic secondary amines.

The preferred a,B-unsaturated esters are esters of fumaric and itaconic acid.

Some of the preferred starting afi-unsaturated ester compounds used in preparing the antioxidant compounds of the present invention are as follows:

a. 3,5-di-tert-butyl-4-hydroxyphenyl acrylate b. 3,5-di-tert-butyl-4-hydroxyphenyl methacrylate CH =C(CH )---CC)OR c. Bis(3,5-di-tert-butyl-4-hydroxyphenyl) fumarate H COORo COOR H i. 4 ,4'-trimethylenedipiperidine HN c 11 CH2 0 Hr In the following table, Table l, the addition of the heterocyclic secondary amine to the a,B-unsaturated ester is carried out by the procedure described above. The purity of all antioxidants was checked either by TLC (thin layer chromatography) or VPC (vapor phase chromatography) and the structure was confinned by IR (infrared) and NMR (nuclear magnetic resonance). Elemental analysis, melting and boiling points, structural formula, and the name of the product are given in Table I.

TABLE L-PROPERTIES AND ANALYSIS OF NOVEL ANTIOXIDANTS Elemental analysis Melting point C.) Calcd. Found crystallized Starting Product Appearance from C H N C H N material Product A White 26-86, 76. 24 8.61 3. 42 76. 67 8. 73 3. 42 (a)+(f) 3,5-di-tert-butyH-hydroryphrnyl 3-l2- (l ,2,3,-i-t -tr:i'

crystals. heptane. hydroisoquinolyflpropinnate.

NGI'TICI'IQCOORQ B White 66. 5-69, 72. 87 9. O9 2. 30 73. 11 9. 14 2. 34 (c)+(c) Bis(3.5-di-tert-butyl-4-hydroxyphenyl) piperidinosucpowder. heptane. cinate.

( N|CHC 0 0 R0 CH2 C O 0 0 C White flakes. 83.5-85, 2. 25 2. 07 (d)+(o) Bis(3,5-di-tart-butyl-4-l1ydroxyphcnyl) 2-(piporidon0- heptane. methyl)succinate.

NCH CHCOOM c Hz 0 o 0 B D White 177-1785, 71.44 9.15 4. 39 70. 93 8. 63 4. 20 (aH-(h) Bis(3,5-di-tert-butyl-4-hydroxyphonyl) 3,3-(1,4-pip0rapowder. ethyl zinediyndipropionate.

acetate.

Table l-Continued Elemental analysis Melting point C.) Calcd. Found crystallized Starting Product Appearance from C H N C H N material Product E d 105-1065, 75. 37 B- 5 (19 75.83 -9 H-(I) (3,5-dl-tert-butyl-4-hydroxyph nyl)2-[2 (1 234- heptanetetrahydrolsoquinolylmethyl)suceinnto. benzene.

NCHiCHCOORo CHzCOOR F 1 153451, 73.68 8.63 4. 73.83 3? 3-87 (c)+(e) Bis (3. -dl-tert-hutyH-hydmr hen n2. heptanepiperazlnyl)]succinat benzene.

@CH:N NCHCOOR CHQCOORI] G "do -46" in- 73.97 9. 7 -67 74. 44 9. 7 3. 1 (aH-(i) B15(3,5-dl-telt-butyL4-hyd hvn 3 Eers), hep- G Q- '-dipiperidin0)dipropir izite? \mmethyl i r-E Ha NcmcHzcoom] H 144-146 74- 39 67 74-50 1 3. 51 (b)+ i) Bi5(3,5-di-tert-hut lhydr h 1 22am th hepmnw 3, 3'(trimethy1ene-4, 4-dipiporidin2) iipropio ri aui benzene.

CH2-ECH2OCH2CH(Cna)COORu] r do 212-213, 12.25 8.84 2.41 72.31 8.50 2.41 (d)+(h) Tetrakis(3,5-di-tert-b t 4.h h t ethyl p p y fit y )disuccinnfig. acetate.

I NCHg(|1HCOOR L CHzCOOR 3 J ..d0 7- 7 73-21 9.29 (d)+(i) T0tl' fiki$(3,fi-dl-tcrt-butyl 4-hyd h g heptane. (trimethylonet, 4-diplperidinodimntliyl) diiucrjinntn, onlonOomonooonol L CHZCOORQ 1 Additional examples of novel antioxidants described in my copending application Ser. No.

represented by Formulas I and II are listed in TAble [1 below. These antioxidants are prepared by the procedure described above. The synthesis of a,B-unsaturated esters containing hindered phenols is fully 738,770, filed on June 21, 1968 now abandoned. The amines employed in preparing the antioxidants reported in TAble II are generally well known with various methods of preparation reported in the literature.

TABLE II.N OVEL ANTIOXIDANTS Starting Materials Antioxidants (product) (0H2)2NH+oH,=c ooormomcoom cmnnonzomooom)cHzcoono (K) 0' NH+0H2=o oooRo)oH2o0oRo o Nomomooonoomcoom (L) s NH+RoOOOOH=CHCO0Ro(trans) s NomoooanoHzooom (M) O NH+RuOCOOH=CHCOORo(trans) O NCH(COOR0)CH2COOR0 (N) +om=oncoono 0 O (0) l CHzCHzCOORo CH3@N NH-l-R OCOOH=CHCOORu ore-@ae NCH(COOR0)CHCOOR0 r NH-l-R OCOOH=CHCOORO :NCH(CO0Ro)CH COOR (Q) CO 0 02H:

TABLE II.- Continued Starting Materials Antioxidants (product) N (R) l1N\ NH+2RGOCOCH=CHCOORO (C RoCIIQCOOR {N N 1 R T I H'2CH2 C(C M000 ncogontcrmcoono r NH +ROOCOOH=CHCOORO (rmorry- Ncmooottooumoon" t-butyl Rn is --0n tbutyl The oxidation of most polymers is so slow at ambient temperatures, even in the absence of antioxidants, that testing of the effects of antioxidants must necessarily be conducted at high temperatures in order to yield results within a convenient period of time. The tests conducted on the materials listed in Table 11 were conducted in a tubular oven with an airflow of 400 feet per minute at an oven temperature of 150 C. The oven ageing is set out in hours.

In preparing the sample for testing, unstabilized polypropylene powder is thoroughly blended with the indicated antioxidant. The blended material is thereafter milled on a two-roller mill at a temperature of 182 C for six minutes after which time the stabilized polypropylene is sheeted from the mill and allowed to cool. The milled polypropylene sheet which has been stabilized is then cut into small pieces and pressed for seven minutes on a hydraulic press at 218 C and 174 psi. pressure. The resultant sheet of mil thickness is then tested for resistance to accelerated ageing in the above described tubular oven.

TABLE III Evaluation of novel Antioxidants in Polypropylene (25 mil), Tubular Oven, 150 C Hours to Fail 0.25% Antioxidant 0.1% Antioxidant Product 0.5% U.V.-2 0.5%U.V.-(2)

0.3% DSTDP.(Z) A 20 70 B 160 540 C 40 150 D 60 260 E 140 520 F 300 600 l 70 350 J 80 300 (l) U.V.-2: an ultraviolet absorber, 2-(3',5-di-t-butyl-2-hydroxyphenyl)-5-chlorobenzotriazole (2) DSTDP: distearylthiodipropionate Results similar to those reported in Table III are obtained when the antioxidants of Table ll are employed together with the indicated synergistsand ultraviolet absorbers.

Product Secondary Antiox. UV Absorber K DSTDP 2-(3'-t-hutyl-2-hydroxy-5- methylphcnyl)-5-chlorobenzotriazole L DLTDP Z-hydroxy-4-n-octyloxybcnzophenone M Tris-nonylphenyl- 4-dodecyloxy-2-hydroxybenzophosphite phenone N Trilauryl trithio- 4-toctylphenyl salicylate phosphite O DLTDP phenylsalicylate P Tris-nonylphenyl- 2,4-dihydroxybenzophenone phosphite Q DSTDP 2-hydroxy'4-methoxybenzophenone R Trilauryl trithio- 5-chloro-2-hydroxybenzophosphite phenone S DLTDP 2-(2'-hydroxy-5-methylphenyl)benzotriazole T DSTDP Dibenzoylresorcinol DLTDP Dilaurylthiodipropionate The tests conducted on the material listed in Table IV were conducted in a rotary oven 4 rpm, at 150 C. The oven ageing is set out in hours. The samples for this test were prepared as described above for the tubular oven tests.

TABLE IV Evaluation of Novel Antioxidants in Polypropylene (25 mil), Rotary Oven, 150 C.

Hours to Fail Product 0.25% Antioxidant 0.1% Antioxidant 0.5% uv-2 0.5% UV-2 0.3% DSTDP s 50 370 H 350 Besides activity in the oven ageing test, the novel antioxidants of the present invention are characterized by excellent color values (no discoloration during the oven ageing test) and good gas fading properties.

The present antioxidants are useful in protecting synthetic polymers such as polypropylene against oxidation in air, thermal degradation or deterioration by including in such substances, a stabilizing amount of the oxidant which will vary between about 0.05 and about 5 percent and preferably, from about 0.1 to about 0.5 percent. The antioxidant can be incorporated into the synthetic polymers using conventional procedures. For example, the antioxidants of the present invention are incorporated into the material to be stabilized by any suitable means such as by milling the antioxidant on hot or cold mill rolls, by mixing it in by the use of a Banbury mixer or other well-known devices of this nature or the antioxidant may be mixed with a polyolefin material in the form of molding powder and incorporated during extrusion or prior to extrusion or during injection molding. The antioxidant may even be incorporated into a solution of the polyolefin material and the solution may then be employed for the formation of films, for wet or dry spinning of fibers, monofilament and the like.

The Examples set out above are to be considered as illustrative of the present invention and are not to be considered as restrictive. It is therefore to be understood that the invention is not limited to the specific embodiments set out above except as defined in the appended claims.

What is claimed is:

1. A compound of the formula wherein R is (linvcr) ulkyl (lower) ulkyl l (lower) alkyl 3. A compound according to Claim 1 wherein R is hydrogenpne of R and R groups is -C H COOR 'wherein m is 0 or 1, and the other is hydrogen.

4. A compound according to claim 1 wherein in For- R and R are hydrogen, R is -COOR and R is 3,5- di-ti-butyl-4-hydroxyphenyl group.

UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE CF CCRRECTION PATENT NO. 3,681,358 DATED August 1, 1972 INV ENTOR(S) Eduard Kleiner It is certified that error appears in the ab0veidentified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 26, "A N" should read A N Column 8, line (3), "NCO2CH(CH3)COORO should read NCH2CH(CH3)COORO Column 7, line 0 of Table III, delete "40" and under 160 in 0,25% Antioxidant Column, insert +0 Column 8, Table IV, above H in Product Column, insert G Column 8, Table Iv, 0.25% Antioxidant Column, '8 50" should read 5O Signed and Scaled this Sixth Day of September 1977 v [SEAL] AIICSI.

RUTH C. MASON Attesting Officer UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT NO. 3,681,358

DATED August 1, 1972 |N\/ ENTOR(S) Eduard Kleiner It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below: 0

Column 2, line 26, A N" should read A N Column 8, line (s), "NCO CH(CH )COOR should read NCH CH(CH )COOR 5 Column 7, line C of Table III, delete +0" and under 160 in 0.25% Antioxidant Column, insert 4O Column 8, Table IV, above H in Product Column, insert G o Column 8, Table IV, 0.25% Antioxidant Column, "s 50" should read 5O r Signed and Scaled this Q" 3 Sixth Day of September 1977 [SEAL] t Attest:

t r RUTH C. MASON LUTRELLE F. PARKER Attesting Oflicer Acting Commissioner of Patents and Trademarks i 

2. A compound according to claim 1 wherein R is
 3. A compound according to Claim 1 wherein R1 is hydrogen,one of R2 and R3 groups is -CmH2mCOOR wherein m is 0 or 1, and the other is hydrogen.
 4. A compound according to claim 1 wherein in Formula I A> N- is C6H5CH2 , R1 and R3 are hydrogen, R2 is -COOR and R is 3,5-di-ti-butyl-4-hydroxyphenyl group. 